Disulfide-linked heterodimeric clusterin is a component of the chicken eggshell matrix and egg white.

Clusterin is a widely expressed secretory glycoprotein which is found in mammals as a disulfide-bonded alpha/beta heterodimer generated by cleavage of the single-chain precursor. In contrast, clusterin occurs in the chicken mainly as an intracellular single-chain form and is not observed in serum. The present report identifies chicken clusterin as a component of the eggshell. This extracellular clusterin originates in the uterine fluid, where it is a disulfide-bonded heterodimer derived from the precursor polypeptide by proteolytic cleavage at the same site as in mammals. Clusterin message expression in the oviduct was measured by real time RT-PCR, and levels were found to be highest in magnum and uterus. Western blotting using protein extracts of oviduct tissues indicated major clusterin production in the magnum, while immunostaining of the oviduct identified clusterin in the tubular glands of the uterus and the magnum. In addition, clusterin was detected in egg white by Western blotting. In the decalcified eggshell, immunofluorescence and colloidal-gold immunocytochemistry revealed that clusterin was predominantly localized in the palisade and mammillary layers, but also in the mantle and core of the inner and outer shell membranes. It has been suggested recently that clusterin acts as an extracellular chaperone. Thus clusterin could function in the uterine fluid to prevent the premature aggregation and precipitation of eggshell matrix components before and during their assembly into the rigid protein scaffold necessary for ordered mineralization.     

A preliminary biomechanical study of cyclic preconditioning effects on canine cadaveric whole femurs

Biomechanical preconditioning of biological specimens by cyclic loading is routinely done presumably to stabilize properties prior to the main phase of a study. However, no prior studies have actually measured these effects for whole bone of any kind. The aim of this study, therefore, was to quantify these effects for whole bones. Fourteen matched pairs of fresh-frozen intact cadaveric canine femurs were sinusoidally loaded in 4-point bending from 50?N to 300?N at 1?Hz for 25 cycles. All femurs were tested in both anteroposterior (AP) and mediolateral (ML) bending planes. Bending stiffness (i.e., slope of the force-vs-displacement curve) and linearity R(2) (i.e., coefficient of determination) of each loading cycle were measured and compared statistically to determine the effect of limb side, cycle number, and bending plane. Stiffnesses rose from 809.7 to 867.7?N/mm (AP, left), 847.3 to 915.6?N/mm (AP, right), 829.2 to 892.5?N/mm (AP, combined), 538.7 to 580.4?N/mm (ML, left), 568.9 to 613.8?N/mm (ML, right), and 553.8 to 597.1?N/mm (ML, combined). Linearity R(2) rose from 0.96 to 0.99 (AP, left), 0.97 to 0.99 (AP, right), 0.96 to 0.99 (AP, combined), 0.95 to 0.98 (ML, left), 0.94 to 0.98 (ML, right), and 0.95 to 0.98 (ML, combined). Stiffness and linearity R(2) versus cycle number were well-described by exponential curves whose values leveled off, respectively, starting at 12 and 5 cycles. For stiffness, there were no statistical differences for left versus right femurs (p?=?0.166), but there were effects due to cycle number (p?相似文献   

Cyclic diguanylate inversely regulates motility and aggregation in Clostridium difficile

Clostridium difficile-associated disease is increasing in incidence and is costly to treat. Our understanding of how this organism senses its entry into the host and adapts for growth in the large bowel is limited. The small-molecule second messenger cyclic diguanylate (c-di-GMP) has been extensively studied in gram-negative bacteria and has been shown to modulate motility, biofilm formation, and other processes in response to environmental signals, yet little is known about the functions of this signaling molecule in gram-positive bacteria or in C. difficile specifically. In the current study, we investigated the function of the second messenger c-di-GMP in C. difficile. To determine the role of c-di-GMP in C. difficile, we ectopically expressed genes encoding a diguanylate cyclase enzyme, which synthesizes c-di-GMP, or a phosphodiesterase enzyme, which degrades c-di-GMP. This strategy allowed us to artificially elevate or deplete intracellular c-di-GMP, respectively, and determine that c-di-GMP represses motility in C. difficile, consistent with previous studies in gram-negative bacteria, in which c-di-GMP has a negative effect on myriad modes of bacterial motility. Elevated c-di-GMP levels also induced clumping of C. difficile cells, which may signify that C. difficile is capable of forming biofilms in the host. In addition, we directly quantified, for the first time, c-di-GMP production in a gram-positive bacterium. This work demonstrates the effect of c-di-GMP on the motility of a gram-positive bacterium and on aggregation of C. difficile, which may be relevant to the function of this signaling molecule during infection.     

Hazardous alcohol consumption is a major factor in male premature mortality in a typical Russian city: prospective cohort study 2003-2009

Introduction

Russia has experienced massive fluctuations in mortality at working ages over the past three decades. Routine data analyses suggest that these are largely driven by fluctuations in heavy alcohol drinking. However, individual-level evidence supporting alcohol having a major role in Russian mortality comes from only two case-control studies, which could be subject to serious biases due to their design.

Methods and Findings

A prospective study of mortality (2003–9) of 2000 men aged 25–54 years at recruitment was conducted in the city of Izhevsk, Russia. This cohort was free from key limitations inherent in the design of the two earlier case-control studies. Cox proportional hazards regression was used to estimate hazard ratios of all-cause mortality by alcohol drinking type as reported by a proxy informant. Hazardous drinkers were defined as those who either drank non-beverage alcohols or were reported to regularly have hangovers or other behaviours related to heavy drinking episodes.Over the follow-up period 113 men died. Compared to non-hazardous drinkers and abstainers, men who drank hazardously had appreciably higher mortality (HR = 3.4, 95% CI 2.2, 5.1) adjusted for age, smoking and education. The population attributable risk percent (PAR%) for hazardous drinking was 26% (95% CI 14,37). However, larger effects were seen in the first two years of follow-up, with a HR of 4.6 (2.5, 8.2) and a corresponding PAR% of 37% (17, 51).

Interpretation

This prospective cohort study strengthens the evidence that hazardous alcohol consumption has been a major determinant of mortality among working age men in a typical Russian city. As such the similar findings of the previous case-control studies cannot be explained as artefacts of limitations of their design. As Russia struggles to raise life expectancy, which even in 2009 was only 62 years among men, control of hazardous drinking must remain a top public health priority.     

Combining the Finite Element Method with Structural Connectome-based Analysis for Modeling Neurotrauma: Connectome Neurotrauma Mechanics

This article presents the integration of brain injury biomechanics and graph theoretical analysis of neuronal connections, or connectomics, to form a neurocomputational model that captures spatiotemporal characteristics of trauma. We relate localized mechanical brain damage predicted from biofidelic finite element simulations of the human head subjected to impact with degradation in the structural connectome for a single individual. The finite element model incorporates various length scales into the full head simulations by including anisotropic constitutive laws informed by diffusion tensor imaging. Coupling between the finite element analysis and network-based tools is established through experimentally-based cellular injury thresholds for white matter regions. Once edges are degraded, graph theoretical measures are computed on the "damaged" network. For a frontal impact, the simulations predict that the temporal and occipital regions undergo the most axonal strain and strain rate at short times (less than 24 hrs), which leads to cellular death initiation, which results in damage that shows dependence on angle of impact and underlying microstructure of brain tissue. The monotonic cellular death relationships predict a spatiotemporal change of structural damage. Interestingly, at 96 hrs post-impact, computations predict no network nodes were completely disconnected from the network, despite significant damage to network edges. At early times ([Formula: see text]) network measures of global and local efficiency were degraded little; however, as time increased to 96 hrs the network properties were significantly reduced. In the future, this computational framework could help inform functional networks from physics-based structural brain biomechanics to obtain not only a biomechanics-based understanding of injury, but also neurophysiological insight.     

Environmental drivers in mangrove establishment and early development: A review

Mangroves have a global distribution within coastal tropical and subtropical climates, and have even expanded to some temperate locales. Where they do occur, mangroves provide a plethora of goods and services, ranging from coastal protection from storms and erosion to direct income for human societies. The mangrove literature has become rather voluminous, prompting many subdisciplines within a field that earlier in the 20th century received little focus. Much of this research has become diffuse by sheer numbers, requiring detailed syntheses to make research results widely available to resource managers. In this review, we take an inclusive approach in focusing on eco-physiological and growth constraints to the establishment and early development of mangrove seedlings in the intertidal zone. This is a critical life stage for mangroves, i.e., the period between dispersal and recruitment to the sapling stage. We begin with some of the research that has set the precedent for seedling-level eco-physiological research in mangroves, and then we focus on recent advances (circa. 1995 to present) in our understanding of temperature, carbon dioxide, salinity, light, nutrient, flooding, and specific biotic influences on seedling survival and growth. As such, we take a new approach in describing seedling response to global factors (e.g., temperature) along with site-specific factors (e.g., salinity). All variables will strongly influence the future of seedling dynamics in ways perhaps not yet documented in mature forests. Furthermore, understanding how different mangrove species can respond to global factors and regional influences is useful for diagnosing observed mortality within mangrove wetlands, managed or natural. This review provides an updated eco-physiological knowledge base for future research and reforestation activity, and for understanding important links among climate change, local physico-chemical condition, and establishment and early growth of mangrove seedlings.     

Nitrogen vs. phosphorus limitation across an ecotonal gradient in a mangrove forest

Mangrove forests are characterized by distinctive tree-height gradientsthat reflect complex spatial, within-stand differences in environmentalfactors,including nutrient dynamics, salinity, and tidal inundation, across narrowgradients. To determine patterns of nutrient limitation and the effects ofnutrient availability on plant growth and within-stand nutrient dynamics, weused a factorial experiment with three nutrient treatment levels (control, N,P)and three zones along a tree-height gradient (fringe, transition, dwarf) onoffshore islands in Belize. Transects were laid out perpendicular to theshoreline across a mangrove forest from a fringe stand along the seaward edge,through a stand of intermediate height, into a dwarf stand in the interior ofthe island. At three sites, three trees were fertilized per zone for 2yr. Although there was spatial variability in response, growth byR. mangle was generally nitrogen (N) -limited in thefringe zone;phosphorus (P) -limited in the dwarf zone; and, N- and/or P-limited in thetransition zone. Phosphorus-resorption efficiency decreased in all three zones,and N-resorption efficiency increased in the dwarf zone in response to Penrichment. The addition of N had no effect on either P or N resorptionefficiencies. Belowground decomposition was increased by P enrichment in allzones, whereas N enrichment had no effect. This study demonstrated thatessential nutrients are not uniformly distributed within mangrove ecosystems;that soil fertility can switch from conditions of N to P limitation acrossnarrow ecotonal gradients; and, that not all ecological processes respondsimilarly to, or are limited by, the same nutrient.